1. Field of the Invention
This document relates to an image processing method and a display device using the same.
2. Discussion of the Related Art
Known display devices include a cathode ray tube, a liquid crystal display (LCD), an organic light emitting diode (OLED), a plasma display panel (PDP), etc. Such a display device has as many sub-pixels of red (R), green (G), and blue (B), respectively, as the maximum number of pixels of an image that can be displayed.
In recent years, in order to reduce power consumption and achieve high resolution in a display device, a technology for reproducing an image close to the original image using pixels whose number is smaller than the resolution of an input image was proposed in U.S. Pat. No. 7,492,379, for example.
In this technology, there are as many G sub-pixels as the actual display resolution and as many R and B sub-pixels, respectively, as half the actual display resolution. In other words, as shown in FIG. 1, this technology provides sub-pixel groups, each sub-pixel group comprising eight sub-pixels: four G sub-pixels; two R sub-pixels; and two B sub-pixels, and repeating in a checkerboard pattern. An R sub-pixel and a G sub-pixel constitute one unit pixel, and a B sub-pixel and a G sub-pixel constitute one unit pixel. Input R, G, and B data RGBi is image-processed into data RGBo corresponding to a pixel array of a display device 2 by a sub-pixel rendering block (SPR) 1. At this point, the SPR block 1 renders all input RGB data RGBi.
This technology uses a diamond filter as shown in FIG. 3 to determine gray scale values of sub-pixels using five sub-pixel values. The weighted value of the central portion of the diamond filter is set to 0.5, and the upper, lower, left, and right peripheral portions surrounding the central portion are respectively set to 0.125. As shown in FIG. 4, in order to determine the R data value Ro of a pixel provided at the intersection of an n-th column Cn and an n-th row Rn, a weighted value of 0.5 applies to the R data value Ri of a pixel provided at the intersection of the n-th column Cn and the n-th row Rn, and a weighted value of 0.125 applies to the R data value Ri of a pixel provided at the intersection of the n-th column Cn and an (n−1)-th row Rn−1, the R data value Ri of the pixel provided at the intersection of the n-th column Cn and an (n+1)-th row Rn+1, the R data value Ri of a pixel provided at the intersection of an (n−1)-th column Cn−1 and an n-th row Rn, and the R data value Ri of a pixel provided at the intersection of an (n+1)-th column Cn+1 and the n-th row Rn, respectively. The same method applies to determine G and B data values Go and Bo.
However, in such conventional technology, an algorithm was developed for a display device, which can be actually be manufactured, has a low resolution. A computational process of this algorithm is complicated because R, G, and B data are all filtered to prevent degradation of a display image. As a result, the degree of reduction of power consumption is small in the actual implementation of a driver IC. Moreover, a color error occurs in a display image due to the diamond filter used for image processing and the sharpness processing using G data, and blurring of the contour of the display image occurs as shown in FIG. 5. Further, as is evident in FIG. 4, particular rows and two rows vertically adjacent thereto are required to determine data values of pixels arranged in the corresponding particular rows, so a minimum of three line memories have to be provided. An increase in line memories causes an increase in product unit cost.